Autofocus device and method

An autofocus method comprising:

• a focal-point-position detecting step of detecting a position of a focal point of a lens;
• a distance-measuring step of measuring a distance to a subject;
• a subject switch determination step of determining a switch of focusing on subjects based on the position of the focal point of the lens detected in the focal-point-detecting step and a measured distance result measured in the distance-measuring step if a restart condition of the focus operation has not yet been satisfied after meeting the position of the focal point of the lens to the in-focus position thereof to stop a focus operation that meets the position of the focal point of the lens to the in-focus position thereof once;
• and
• a focus-readjusting step of restarting the focus operation based on a determination result of the switch of focusing on subjects in the subject switch determination step to drive the position of the focal point of the lens to an in-focus position thereof based on a measured distance result by the distance measurement sensor.

A computer program product that allows a computer to execute an autofocus method, said method comprising:

• a focal-point-position detecting step of detecting a position of a focal point of a lens;
• a distance-measuring step of measuring a distance to a subject;
• a subject switch determination step of determining a switch of focusing on subjects based on the position of the focal point of the lens detected in the focal-point-detecting step and a measured distance result measured in the distance-measuring step if a restart condition of the focus operation has not yet been satisfied after meeting the position of the focal point of the lens to the in-focus position thereof to stop a focus operation that meets the position of the focal point of the lens to the in-focus position thereof once;
• and
• a focus-readjusting step of restarting the focus operation based on a determination result of the switch of focusing on subjects in the subject switch determination step to drive the position of the focal point of the lens to an in-focus position thereof based on a measured distance result by the distance measurement sensor.